This invention relates to a bleaching formulation suitable for removal of stains or dirt from clothes or rigid surfaces such as tableware, glassware, plastics, and artificial teeth, hair bleaching, wood pulp bleaching, and the like.
It is a well-known technique to use peroxy bleaching agents, such as hydrogen peroxide, in laundering. Peroxy bleaching agents are used at high temperature and effective for removal of stains of tea, coffee, wine and fruit. Because the peroxy bleaching agents drastically reduce their effect at 60xc2x0 C. or lower, a combined use of transition metal complexes as an activator catalyzing peroxide oxidation reactions has been studied. For example, JP-B-7-65074 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) discloses a manganese complex having a cyclic polyamine as a ligand; JP-W-11-507689 a cobalt ammine complex; JP-A-8-67687 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-W-11-515049 (the term xe2x80x9cJP-Wxe2x80x9d as used herein means an unexamined published international patent application) a manganese or cobalt Schiff base derivative complex; WO95/34628 and WO97/48710 an iron complex having a pyridylmethylamine derivative as a ligand; and WO98/03625 an iron complex with a tetraamide derivative ligand. However, these proposals have their several disadvantages. For example, some combinations fail to develop bleaching performance, and some combinations exhibit bleaching performance but damage fiber or bleach out even dyes. Some complexes are labile, and some other complexes are costly.
In order for a bleaching composition containing a transition metal complex as an activator to develop bleaching activity, it is required that the complex itself be stable in an aqueous bleaching solution and capable of reacting with a source of hydrogen peroxide to produce a kind of oxidation active species which reacts with stains. Another factor which also governs the bleaching performance of the bleaching composition is whether the complex has easy access to objects to be bleached (fiber (cloth) and rigid surfaces, e.g., glassware and earthenware). Seeing that the objects to be bleached and most of their stains are negatively charged (anionic), and peroxides such as hydrogen peroxide are also anionic, it is advantageous for the activator itself be cationic in view of a favorable electrostatic interaction as suggested in JP-A-1-97267. In fact, the manganese complex of JP-B-7-65074 and the cobalt complex of JP-W-11-507689 are cationic so as to have good access to fiber (cloth). Nonetheless the bleaching compositions containing these complexes cannot get rid of the above-described disadvantages. On the other hand, the iron complex of WO98/03625, being anionic, is not considered to have easy access to objects to be bleached and to develop expected activity.
An object of the present invention is to provide a bleaching composition containing an anionic activator (catalyst) in which a peroxy bleaching agent exhibits improved performance even in low temperatures.
The present inventors have found that a combination of a cationic compound and an anionic bleaching activator provides a bleaching formulation exhibiting markedly improved bleaching performance.
The present invention provides a bleaching formulation comprising (a) a peroxy bleaching agent selected from hydrogen peroxide and a peroxide or an organic peracid capable of generating hydrogen peroxide in an aqueous solution, (b) an anionic bleaching activator containing a metal, and (c) a cationic compound.
The invention also provides a method of bleaching an object, which comprises using the above-described bleaching formulation according to any of procedures (i) to (iii):
(i) The object is bleached with a mixture of components (a), (b) and (c).
(ii) The object is pre-treated with a composition containing component (c) and then bleached with a composition containing components (a) and (b).
(iii) The object is pre-treated with a composition containing components (b) and (c) and then bleached with a composition containing component (a).